737-800 aileron position
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737-800 aileron position
I just noticed that unlike most planes, the 737 has the ailerons well inboard of the wingtip. I wonder why boeing did that. It's notorious for relatively high approach speeds. Wouldn't it help to move the ailerons further outboard (which would enable them to be smaller), and add a bit more flaps to lower the approach speed?
Does anyone have any insight as to why Boeing designed the wing that way?
Does anyone have any insight as to why Boeing designed the wing that way?
Perhaps to reduce the twisting load on the wing structure? AFAIK, the only bigger Boeing that has only one set of ailerons (i.e. not high speed/low speed pairs) is the 757. Even the 727 was fitted with high speed ailerons, though its span is sevral feet less than that of the 737NG.
You'd need one of the design team to be certain of the original reason, but the usual reason for inboard ailerons are to reduce torsion moments on the wing structure, allowing a less stiff (and thus lighter) wing. IIRC the original use would be the F100.
Moving the ailerons away from the tips also reduces flutter risks.
Many airliners use spoilers rather than or in addition to ailerons for roll control (also to reduce torsion moments on the wing structure). In some cases the spoilers and ailerons are scheduled at different points in the flight envelope while in other the spoilers are the primary controls and the ailerons just provide "feel" (concept originally developed for the XF-11, I believe).
Remember that most airliners of this lineage have torsionally "flexible" wings (to reduce weight) and use the podded engines as mass-dampers to mitigate the flexibility.If an aeroplane has reduced wing structure weight in this way you wouldn't want to add further flap area outboard, as that would add further steady-state torsion loads which would require a stiffer, heavier wing again.
It's all about finding the optimum trade-off between performance and weight.
Moving the ailerons away from the tips also reduces flutter risks.
Many airliners use spoilers rather than or in addition to ailerons for roll control (also to reduce torsion moments on the wing structure). In some cases the spoilers and ailerons are scheduled at different points in the flight envelope while in other the spoilers are the primary controls and the ailerons just provide "feel" (concept originally developed for the XF-11, I believe).
Remember that most airliners of this lineage have torsionally "flexible" wings (to reduce weight) and use the podded engines as mass-dampers to mitigate the flexibility.If an aeroplane has reduced wing structure weight in this way you wouldn't want to add further flap area outboard, as that would add further steady-state torsion loads which would require a stiffer, heavier wing again.
It's all about finding the optimum trade-off between performance and weight.
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The 738 has a roughly six meter longer wing span than the 737 classic. As far as i kow the position of the aileron relative to the fuselage was not changed, they just added a bit more wing outboard of the previous wing span. Same for wing anti ice, the last outboard slat, which covers that added span, is not heated on the 738, they simply didn't increase the length of the bleed duct.
All probably for the reasons mentioned above.
All probably for the reasons mentioned above.
I "beefed up structure" would be significantly heavier, so there is no guarantee that it would achieve lower landing speeds even with longer flaps.
And it's not so much a matter of "money talks" as "this is the target market". There is no point in building an airliner whose specific operating costs are higher than the opposition. Airlines operate on a financial knife-edge anyway, and there's no slack available to accommodate a less cost-effective aeroplane.
The design of any aeroplane is a series of trade-offs between weight and cost, reliability and cost, reliability and weight, maintainability and cost or weight, take-off performance and cruise fuel consumption, landing speeds and operating cost, landing speeds and cruise speed, landing speeds and reliability etc etc. All of these are studied in nauseating detail before the basic configuration is frozen, and revisited at every design verification stage.
If they don't do this then they end up with a product no one wants to buy, and everyone goes bust. The staff are thrown out on the streets to starve in the gutter, turning to drink and drugs before deciding to end it all by hijacking an airliner and flying it into a nuclear power station, causing massive radiation leaks and the end of all life on the planet.
Against that I'd suggest a few extra knots on the approach speed is probably an acceptable trade-off - n'est pas?
And it's not so much a matter of "money talks" as "this is the target market". There is no point in building an airliner whose specific operating costs are higher than the opposition. Airlines operate on a financial knife-edge anyway, and there's no slack available to accommodate a less cost-effective aeroplane.
The design of any aeroplane is a series of trade-offs between weight and cost, reliability and cost, reliability and weight, maintainability and cost or weight, take-off performance and cruise fuel consumption, landing speeds and operating cost, landing speeds and cruise speed, landing speeds and reliability etc etc. All of these are studied in nauseating detail before the basic configuration is frozen, and revisited at every design verification stage.
If they don't do this then they end up with a product no one wants to buy, and everyone goes bust. The staff are thrown out on the streets to starve in the gutter, turning to drink and drugs before deciding to end it all by hijacking an airliner and flying it into a nuclear power station, causing massive radiation leaks and the end of all life on the planet.
Against that I'd suggest a few extra knots on the approach speed is probably an acceptable trade-off - n'est pas?
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Against that I'd suggest a few extra knots on the approach speed is probably an acceptable trade-off - n'est pas?
Especially when airlines always try and land at less than max flap settings to save fuel.
Especially when airlines always try and land at less than max flap settings to save fuel.
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The 738 has a roughly six meter longer wing span than the 737 classic. As far as i kow the position of the aileron relative to the fuselage was not changed, they just added a bit more wing outboard of the previous wing span. Same for wing anti ice, the last outboard slat, which covers that added span, is not heated on the 738, they simply didn't increase the length of the bleed duct.
All probably for the reasons mentioned above.
All probably for the reasons mentioned above.
